Method for improving charging criteria in a mobile telephone network

ABSTRACT

Charging criteria in a mobile telephone network may be improved by choosing one cell or a group of several cells of the mobile telephone network as a group of special cells. The cells of the group may be located in the areas of different MSC&#39;s. When a call is being established, a service control point SCP located in an intelligent network analyses whether the location cell of a calling subscriber and that of a called subscriber belong to the group of special cells. Subscriber numbers of the subscribers may also be taken into account. The service control point SCP then applies a special charging criterion determined for the group. In a case where the location cell of the calling subscriber and that of the called subscriber are located in separate MSC areas (MSC1/SSP1, MSC2/SSP2), the information on the location cell of the called subscriber is transmitted to the service control point (SCP1) connected to the mobile switching center (MSC1/SSP1) of the calling subscriber either directly or in a message in accordance with signalling used between MSC&#39;s.

This application is the national phase of international applicationPCT/F195/00706 filed Dec. 21, 1995 which designated the U.S.

BACKGROUND OF THE INVENTION

This invention relates to charging criteria used in a mobile telephonenetwork for determining a price for a call between two subscribers.

In a fixed telephone network, a calling subscriber is aware of thecharging criteria for the call already upon dialing the number ofanother, B subscriber as charging depends on whether it is a question ofa local call, a long-distance call or an international call. In PBXexchanges (Private Branch Exchange) connected to a fixed telephonenetwork, or in PABX networks, internal calls are free of charge. Incordless PBX's, part of the subscriber lines are replaced with a radioconnection. In cordless PBX's, there are both fixed and cordlessextensions. Cordless PBX's thus allow the users of cordless telephonesmobility, which depends on the coverage area of cordless base stations.A coverage area typically covers the indoor premises of an officebuilding.

In mobile telephone networks, which enable a high degree of mobility,the charging criteria used in a fixed network cannot be used as suchowing to the structure and the mode of operation of the network. In thefollowing, the structure and the operation of a mobile telephone networkwill be illustrated by means of a prior art GSM mobile telephone networkshown in FIG. 1. Communication between a mobile station MS locatedwithin a cell, and the network takes place over the radio path via abase transceiver station (BTS). Base transceiver stations are connectedto a base station controller (BSC), whose tasks include e.g. managementof radio channels, as well as changeover procedures. One base stationcontroller BSC thus controls a number of base stations BTS. The locationof a mobile station is known with the accuracy of a so-called locationarea (LA) composed of a few cells. A mobile station may move within thelocation area without a need to update the location information relatedto it. A plurality of base station controllers are connected to onemobile services switching centre MSC, which performs the main switchingfunctions of the mobile telephone network. The area of the cellscontrolled by the mobile services switching centre is termed as an MSCarea, and all the calls originating or terminating within this area areswitched via this MSC. Furthermore, the MSC connects the mobiletelephone network to external networks.

The mobile telephone network also contains data bases of differentkinds. In a Home Location Register (HLR), subscriber data is permanentlystored regardless of the current location of the subscriber. The HLRcontains the MSISDN number of the subscriber, the International MobileSubscriber Identity code IMSI to be used inside the network, subscriberservice data, and routing information on a Visitor Location RegisterVLR. The Visitor Location Register VLR is integrated to all presentMSC's, and it is used for recording the subscriber data obtained fromthe HLR for the duration of the visit of the subscriber to the area ofthe VLR. The VLR contains the subscriber's IMSI, MSISDN, subscriberservice data, and the location area identifier LAI that has been used bythe subscriber for updating the location information. The location ofthe subscriber is thus known with the accuracy of a location area.

In the following, call establishment in a mobile telephone network willbe disclosed for understanding the charging criteria: When a subscriberswitches on his mobile station MS, e.g. in cell A (FIG. 1), it signalsan updating request to a base station, which request is directed to amobile services switching centre MSC1, and further to a visitor locationregister VLR. The request searches an IMSI from a home location registerHLR. Thereafter, once it has been made sure in the signalling betweenthe VLR and the mobile station that the IMSI is correct, the VLR sendsan update request to the HLR, which will send the subscriber data to theVLR. Now the location of the subscriber is updated, i.e. the HLR knowsthe address of the VLR, and the VLR knows in which location area LAI thesubscriber is located.

When a subscriber A calls a subscriber B located in a location area 22of a second mobile services switching centre MSC2, he dials the MSISDNnumber of subscriber B into his mobile station. Signalling phases takingplace after this are indicated with ringed numbers in FIG. 1, followedby the number to be switched in the phase in question. Indication MAP,TUP/ISUP represents the protocol to be used in the signalling inquestion. Next, mobile station MS-A sends base station 5 a messagecontaining the dialed number, phase 1. When MSC1 receives the message,it analyses it and checks whether the request may be accepted. As a partof the check, the subscriber data of subscriber A is searched from theVLR of the MSC1, said data being recorded in connection of theabove-mentioned location updating. If the request is accepted, MSC1 willsend an interrogation message to the HLR, said message containing theMSISDN number of the mobile station of subscriber B, phase 2. On thebasis of this number, the HLR searches the data on subscriber B, thedata containing the address of the current VLR of subscriber B. Next theHLR asks the VLR to provide a roaming number by sending information IMSIto it, phase 3, "whereafter the VLR sends the roaming number MSRN to theHLR, phase 4. The roaming number MSRN is sent from the HLR to MSC1,phase 5. Thereafter, it is possible to route the call from MSC1 to MSC2on the basis of the roaming number MSRN received from the VLR, phase 6.The mobile services switching centre MSC2 of subscriber B asks the VLRincorporated into it for the subscriber data on subscriber B. Thesubscriber data indicates the location area LAI of subscriber B, so thatMSC2 is able to send a paging message via the base station controller 2in question (phase 7) to cells f, g, and h in the location area. Oncethe mobile station MS-B of subscriber B has answered the paging, a callwill be established to subscriber B. It must be noted that only afterthe mobile station of subscriber B has answered the paging message,mobile services switching centre MSC2 knows the location of subscriber 2to the accuracy of one cell.

A Service Switching Point (SSP) of an Intelligent Network (IN) may alsobe connected to a mobile services switching centre. The physicalarchitecture of an intelligent network is shown in FIG. 2. The serviceswitching point SSP provides the user access to the network, and handlesall the necessary switching functions. It is capable of detecting theservice requests of the intelligent network. Functionally, the SSPcomprises the call management and service switching functions. A ServiceControl Point (SCP) comprises service programs, which are used forproducing services of the intelligent network. A Service Data Point(SDP) is a database comprising data of the subscriber and the network,which data is used by the service programs of the network for providingindividual services. The SCP may use the services of the SDP directly orvia a signalling network. An Intelligent Peripheral (IP) providesspecial functions, such as announcements, as well and audio and multidialling detection. The Service Switching and Control Point (SSCP)consists of an SCP and an SSP in one node. The tasks of an ServiceManagement Point (SMP) include database management, controlling andtesting of the network, and collecting network information. It may beconnected to all other physical entities. A Service Creation EnvironmentPoint (SCEP) is used for determining, developing and testing theintelligent network, as well as for feeding services to the SMP. AnAdjunct (AD) of a service functionally corresponds to the ServiceControl Point SCP, but it is directly connected to the SSP. A ServiceNode SN may control the services of the intelligent network and carryout data transmission with the users. It communicates directly with oneor more SSP's. A Service Management Access Point (SMAP) is a physicalentity providing the users a connection to the SMP.

A Basic Call State Model (BCSM) determined in connection with theIntelligent Network describes different phases of call processing andcontains points where call processing may be interrupted for starting aservice of the Intelligent Network. It identifies the detection pointsin a call and connection process, in which the IN service logic entitiesmay interact with basic call and connection management functions.

On account of an intelligent network it is possible to provide to theuser of a fixed network and a mobile telephone network a large number ofvarious services, such as a Private Numbering Plan (PNP), which enablesthe use of private numbers, and a Closed User Group, in which the usersmay call only the subscribers belonging to the same group. Furthermore,Private Branch Exchanges (PBX) may be connected to a mobile telephonenetwork. A separate numbering block is determined for PBX subscribers inthe numbering space of an MSC.

In a mobile telephone network in accordance with the prior art, allcells are equal as far as the price of a call is concerned. In mobiletelephone networks, the price of a call is based on whether it is aquestion of a call between a mobile station and a fixed network, or amobile-to-mobile call. Due to the mobility of mobile stations, the basicrule of charging is to charge a subscriber A for the connection betweenhim and the home network of a subscriber B, and to charge subscriber Bfor the connection between his present location and his home network.This is considered fair, as, in accordance with call setup describedabove, neither the calling subscriber nor the first mobile servicesswitching centre knows the location of subscriber B, i.e. in which cellthe subscriber is located when the call setup is being started.

To increase the flexibility of the charging criteria, it is possible toset a special charging parameter, which will make it possible to apply alower tariff to the calls made from the number related to the parametersduring off-peak times, and correspondingly, a higher tariff thannormally during the peak times. This parameter will make the chargingcriterion time-dependent, but, in other respects, the charging willfollow the above-mentioned principles.

When the charging criterion of mobile telephone networks described aboveare compared with those of the fixed network, a few problems arise.Since all the cells are equal from the point of view of the mobiletelephone network, no other charging criteria may be offered todifferent groups of users except for flexibility based on the time ofthe day. The distance between the calling and the called subscriber, orthe location of the called subscriber cannot be taken into account inreal time when determining the charging criteria. Special chargingcriteria are not available for certain intra-cell calls or for certaininter-cell calls.

SUMMARY OF THE INVENTION

An object of this invention is to provide a method for improving thecharging criteria, and to solve the above-mentioned problems.

In a method of the invention, one cell or a group of several cells ischosen as a group of special cells. The service control point SCP of theintelligent network has the information on the group and its cells. Inthe SCP, there is a service program for charging criteria for analysingwhether the location cell of a calling subscriber and that of a calledsubscriber belong to the group of special cells. If that is the case,the charging criteria determined for the group will be applied to thecall.

In accordance with a preferred embodiment, a subscriber group consistingof subscriber numbers may be determined. The Service Control Point SCPof the intelligent network has the information on the subscriber groupand its subscriber numbers. When the service program for chargingcriteria is determining the charging criterion, it uses both the numberand the location cell of the calling subscriber and those of the calledsubscriber as parameters. For instance, if at least one parameter refersto the group of special cells and to the group consisting of thesubscriber group, the special charging criterion determined for the casemay be applied.

In accordance with a preferred embodiment, when the location cell of thecalling subscriber and that of the called subscriber are situated withinseparate MSC areas, the information on the location cell of the calledsubscriber is transmitted either every time, only on request from theMSC of the called subscriber to the service control point SCP connectedto the MS of the calling subscriber.

In accordance with a preferred embodiment, where the location cell ofthe calling subscriber and that of the called subscriber are situated inseparate MSC areas, the information on the location cell of the calledsubscriber is transmitted either every time or only on request first tothe MSC of the calling subscriber, and further to the service controlpoint SCE connected thereto.

In accordance with a preferred embodiment, when the location cell of thecalling subscriber and that of the called subscriber are situated inseparate MSC areas, the information on the location cell of the calledsubscriber is transmitted either every time, or only on request from theservice control point SCP connected to the MSC of the called subscriberto the service control point SCP connected to the MSC of the callingsubscriber.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be disclosed in more detail withreference to the attached drawings in which

FIG. 1 shows the design of a prior art mobile telephone network,

FIG. 2 shows the architecture of an intelligent network,

FIG. 3 shows a first embodiment of the invention,

FIG. 4 shows a second embodiment of the invention, and

FIG. 5 shows a third embodiment of the invention.

DETAILED DESCRIPTION

Reference is still made to FIG. 1. In accordance with the invention,cells a, c, d and e are chosen as the group of special cells. Separatecharging criteria may be determined for intracell and intercell callswithin this group.

Cells a and c are controlled by the same base station controller, andthey thus belong to the same location area, whereas cells d and e arecontrolled by separate base station controllers (base stationcontrollers 3 and 4), and they thus belong to separate location areas.The base station controllers of the base stations of the cells, however,are connected to the same mobile services switching centre MSC1/SSP1,and the service control point SCP1 connected thereto contains theinformation on which cells form the group of special cells. Supposesubscriber A is located in cell a and subscriber B is located in cell d.In accordance with call setup set out above, mobile services switchingcentre MSC1/SSP1 receives the information on the number and locationcell of subscriber A once the mobile station of the subscriber has senta call setup message. SCP1 analyses whether the location cell a ofsubscriber A belongs to the group of special cells and detects that isthe case. Mobile services switching centre MSC1/SSP1 receives theinformation on the location cell of subscriber B once subscriber B hasreplied to the paging message sent to its location area. Service controlpoint SCP1 analyses whether the location cell d of subscriber B belongsto the group of special cells. If SCP1 detects that the location cellsof either or both of the subscribers belong to the group of specialcells, service control point SCP1 chooses the charging criteriondetermined for the group of special cells as the charging criterion tobe applied.

When it is desirable to limit the subscriber numbers to which thecharging criteria determined for the group of special cells may beapplied, a restricted subscriber group is defined. It is a list ofsubscriber numbers recorded into the service data point SDP of theservice control point SCP. During call setup described above, SCP1connected to the mobile switching centre MSC1/SSP1 of subscriber A findsout by means of a charging criterion analysis what is the relation ofsubscribers A and B to the restricted subscriber group, and what is therelation of the location cells of the subscribers to the group ofspecial cells. An individual charging criterion may be determined foreach combination. The number of combinations may be limited so that, forexample, if both the subscriber number and the location cell of eitherof the subscribers or both of the subscribers belong to the restrictedsubscriber group and to the group of special cells, individual chargingcriteria will be applied. The numbers of the subscriber group may alsobe determined by means of the Private Numbering Plan PNP.

The cells belonging to the group of special cells may be distributed inthe areas of several mobile services switching centres. A cell f inlocation area 22 of MSC2/SSP2 is determined to the group of specialcells in addition to the above-mentioned cells a, c, d, and e, shown inFIG. 1. Every SCP has information on which cells belong to the group ofspecial cells at least in the area of the MSC connected to it.Alternatively, each SCP may have information on all the cells located inthe different MSC areas of the mobile telephone network and forming thegroup of special cells. Suppose subscriber A is located in cell a, andsubscriber B is in cell f of MSC2/SSP2. In accordance with call setupdescribed above, MSC1/SSP1 receives the information on the number andthe location cell of subscriber A once the mobile station of thesubscriber has sent a call setup message. SCP1 connected to MSC1/SSP1checks whether the location cell a of subscriber A belongs to the groupof special cells and detects this is the case. In accordance with callsetup described above, MSC2/SSP2 receives the information on thelocation cell of subscriber B once the mobile station MS-B of subscriberB has replied to the paging message sent in its location area 22. Inorder that SCP1 could take into account upon determining the chargingcriterion whether the location cell f of subscriber B belongs to thegroup of special cells, SCP1 must have the information on the locationcell of subscriber B before a call is connected between the subscribers.Thus, special charging criteria may be applied in real-time from thebeginning of the call to internal calls of the group, as well as callsoriginating from and terminating in the group. For transmitting theinformation on the location cell, three different embodiments will bedisclosed below.

The information to be transmitted from MSC2/SSP2 to the SCP1 connectedto the MSC1/SSP1 of subscriber A, concerning the location cell ofsubscriber B may be just a piece of information on the location cellwhich has been found out after the mobile station MS-B of subscriber Bhas replied to the paging message sent within its location area. In sucha case, SCP1 first analyses on the basis of the cell informationreceived on whether the location cell of subscriber B belongs to thegroup of special cells, and thereafter determines the chargingcriterion.

Alternatively, the analysis for finding out whether the location cell ofsubscriber B belongs to the group of special cells or not may be carriedout already in SCP2 connected to MSC2/SSP2. In that case, theinformation on the location cell to be transmitted to SCP1 is the resultof said analysis, and SCP1 may immediately utilize the result receivedfor determining the charging criterion.

The above description does not state any trigger criteria for triggeringthe use of a charging criteria service program provided by theintelligent network when the trigger criteria is fulfilled. There may beseveral trigger criteria. A trigger criteria may be e.g. the IN serviceclass of a subscriber (i.e. the subscriber belongs to a specialsubscriber group, e.g. to the PNP group), or it is possible to startusing the IN service in the connection of each call.

In a case where the calling or the called subscriber is a PBXsubscriber, it is possible to determine the PBX subscriber a virtualcell to be used when it is necessary to take a PBX subscriber intoaccount when determining the charging criteria. This virtual cellinformation, or information related to charging is of no importance tothe radio system. Virtual cell information may also be applied to a PSTNsubscriber. When it is a question of a PABX or a PSTN network, thevirtual cell information may be stored in the mobile services switchingcentre to which these networks are connected.

Everything that has been said about the case where a group of specialcells is located within the area of one MSC is also applicable as suchto a case in which the cells of the special group are distributed in theareas of several MSC's. It is thus possible to form a restricted groupof subscribers, to use a private number etc.

In the following, three different embodiments for transmitting theinformation on the location cell to the SCP connected to the MSC ofsubscriber A will be disclosed.

FIG. 3, showing only the network components essential to the invention,illustrates a first embodiment, according to which the information onthe location cell of subscriber B is transmitted to the SCP1 connectedto the MSC1/SSP1 of subscriber A. The identifier of the service programdetermining the address of SCP1 and the charging criterion may beobtained by MSC2/SSP2 from MSC1/SSP1 e.g. as follows:

a) in a call setup message IAM in accordance with ISUP either in a field"Called Party Number", in a field "Generic Number", whereby the addressand identifier information is inserted in these fields, or a new fieldor new fields are defined in the message for the address and identifierinformation,

b) in a new ISUP (TUP) message intended for this purpose, transmittedfrom the MSC of subscriber A to the MSC of subscriber B,

c) in a new pair of ISUP messages intended for this purpose, wherein theMSC of subscriber B (upon detecting that e.g. the cell of subscriber Bbelongs to the group of special cells) first sends the MSC of subscriberA an interrogation on whether the MSC of subscriber A needs this cellinformation. The MSC of subscriber A may response to the inquiry bysending the MSC of subscriber B the information on a service controlpoint and a service program, whereby the new message will contain a SCPid and a Correlation Id.

By means of a call setup message, it is also possible to ask for theinformation on the location cell of subscriber B separately. This is analternative for sending the information on the location cell every time.Once the mobile switching centre MSC2/SSP2 has found out in which cellthe subscriber is located, it may ask the service control point SCP2 toanalyse the cell information. This must be done it each service controlpoint SCP has an information regarding only the special cells of themobile switching centre connected to the SCP in question. Theinformation on the location cell of subscriber B, either the cellinformation only, or the information on whether the cell possiblybelongs to the group of special cells, obtained as a result of theanalysis, is sent from MSC2/SSP2 to the SCP1 connected to MSC1/SSP1. Theinformation on the location cell of subscriber B is sent, e.g., by meansof an Assist Request Instruction procedure in accordance with an INAPprotocol by inserting the information in a field "extensions" of theprocedure, or by defining a separate message in the INAP fortransmitting this information, in which message the information is alsotransmitted on the SCP in question (a so-called SCP id) and on theservice program (a so-called Correlation id) related to it. OnceMSC1/SSP1 has received an answer message sent by MSC2/SSP2, as is wellknown, in response to that subscriber B has answered the call, it willreport it to its SCP1. The answer message will initiate charging of thecall.

FIG. 4 shows a solution in accordance with a second embodiment fortransmitting information on the location cell of subscriber B. Itdiffers from the solution of the first embodiment shown in FIG. 3 inthat the information on the location cell of subscriber B is firsttransmitted to the MSC1/SSP1 of subscriber A, and further to SCP1. Inthis embodiment, it is not necessary to provide the address of SCP1 andthe identifier of the service program determining the charging criterionin the call setup message, but it is possible to transmit an informationon the location cell of subscriber B in the message provided that theinformation is not required every time. The information on the locationcell of subscriber B is sent in a prior art message in accordance withsignalling used between mobile switching centres, or a separate messagemay be created for it. The use of messages in accordance with signallingused between mobile switching centres for transmitting information onthe location cell is disclosed in a parallel patent application FI946091 filed simultaneously with the present application.

In accordance with the above-mentioned parallel patent application, theinformation on a location cell may be inserted e.g. in an AddressComplete message, which is sent by the MSC of subscriber B to the MSC ofsubscriber A after a successful paging of the called subscriber.Alternatively, the information on the location cell may be added to theanswer message, which is sent by the MSC of subscriber B to the MSC ofsubscriber A in response to that subscriber B has answered the call. Theinformation on the location cell, added to the answer message, may alsobe used for confirming or canceling a previous information on thelocation cell, received in an Address Complete Message. In ISUPsignalling, the Initial Address Message is IAM, Address Complete Messageis ACM and Answer Message is ANM. In TUP signalling, the abbreviationfor the answer message is ANU (Answer signal, unqualified), ANC (Answersignal, charge), or ANN (Answer signal, no charge). Depending on theapplication, other messages may alternatively also be used, such as CallProgress, Connect.

Once the information on the location cell is received in one of theabove-mentioned messages, MSC1/SSP1 will report it to SCP1, which nowhas all the information for determining the charging criterion. OnceMSC1/SSP1 has received the answer message, it will also report themessage to SCP1, which will then determine the charging criterion.

FIG. 5 shows a third embodiment for transmitting the information on thelocation cell of subscriber B to SCP1. After MSC2/SSP2 has found out thelocation cell of subscriber B as described above, SCP2 reports theinformation on the location cell of subscriber B to the SCP1 connectedto MSC1/SSP1. The information on the address has been obtained by SCP2in the call setup message.

Once the MSC of subscriber A has obtained a normal answer message fromthe MSC of subscriber B, it will report it to SCP1, which will determinethe charging criterion. The call will be charged on the basis of thischarging criterion. This embodiment requires that there is a signallingconnection between the SCP's. In an intelligent network conceptual modelcalled CS1 (Capability Set 1) determined by CCITT, no signallingconnection is defined between the SCP's, but in a model CS2 which ispresently being developed, a signalling connection is underconsideration. In the signalling connection, e.g. a MAP protocol or anINAP protocol could be employed by defining in them a new message fortransmitting the information on the location cell.

Regardless of the method of transmitting information on the locationcell, the information must arrive at the SCP connected to the MSC ofsubscriber A along with the answer message at the latest in order thatcharging would have sufficient time to utilize the information on thelocation cell of subscriber B.

When a PABX or a PSTN subscriber is participating in a call, theabove-mentioned messages or other known signalling messages will be usedfor transmitting virtual cell information from the MSC of the calledsubscriber to the MSC of the calling subscriber. For this purpose it isalso possible to create separate signalling messages if necessary.

With the method of the invention, it is possible to implement a"wireless office" system, where a group of cells is formed of cellsincluding various geographically distant units of a community, company,etc.

The above explanation and the figures associated therewith are onlyintended to illustrate the present invention. Different variations andmodifications of the invention will be obvious to a person skilled inthe art without deviating from the scope and the spirit of the inventionset forth in the attached claims.

What is claimed is:
 1. A method for improving charging criteria in acellular mobile telephone network wherein a service switching point SSPis connected to a mobile switching centre MSC for providing subscribersaccess to services of a service control point SCP, comprisingforming agroup of special cells comprising at least one cell of the cells of themobile telephone network, forming a restricted subscriber group based onsubscriber numbers, forming a charging criterion service at the servicecontrol point SCP, determining, at the service control point, based oncell information sent to the service control point from the serviceswitching point during a call setup, whether a location cell of asubscriber participating in a call belongs to the group of specialcells, determining at the service control point whether a subscribernumber of a subscriber participating in the call belongs to therestricted subscriber group, and the service control point applying,according to the charging criterion service, a charging criteriondetermined for the group of cells to the call when at least one of thesubscribers belongs to the group of cells or the subscriber numberassociated with the subscriber belongs to the restricted subscribergroup.
 2. A method as claimed in claim 1, wherein the information on thelocation cell of a called subscriber is transmitted in connecting thecall.
 3. A method as claimed in claim 1, wherein the information on thelocation cell of a called subscriber is transmitted in response to arequest sent by the MSC of the calling subscriber in a call setupmessage during call setup.
 4. A method as claimed in claim 1, whereinthe information on the location cell of a called subscriber is insertedin a message sent by the mobile switching centre of the calledsubscriber once the called subscriber has responded to a paging messageand wherein the information on the location cell is further forwardedfrom the mobile switching centre of the calling subscriber to a servicecontrol point connected thereto.
 5. A method as claimed in claim 1,wherein the information on the location cell of a called subscriber isinserted in a message sent by the mobile switching centre of the calledsubscriber once the called subscriber has answered a call, and whereinthe information on the location cell is further forwarded from themobile switching centre of the calling subscriber to the service controlpoint connected thereto.
 6. A method as claimed in claim 1, wherein anew message is formed for transmitting information on the location cellfrom the mobile switching centre of a called subscriber to the mobileswitching centre of the calling subscriber, and wherein the informationon the location cell is further forwarded from the mobile switchingcentre of the calling subscriber to the service control point connectedthereto.
 7. A method as claimed in claim 1, wherein the information onthe location cell of a called subscriber is transmitted from the mobileswitching centre of the called subscriber to the service control pointconnected to the mobile switching centre of the calling subscriber.
 8. Amethod as claimed in claim 1, wherein a message is transmittedcontaining the information on the location cell of a called subscriberfrom the service control point connected to the mobile switching centreof the called subscriber to the service control point connected to themobile switching centre of the calling subscriber.
 9. A method asclaimed in claim 7, wherein the information on the service switchingpoint connected to the mobile switching centre of the calling subscriberand a service program related thereto are added to a call controlmessage sent by said mobile switching centre to the mobile switchingcentre of the called subscriber.
 10. A method as claimed in claim 7,wherein the information on the service switching point connected to themobile switching centre of the calling subscriber and a service programrelated thereto are inserted in a new message sent by said mobileswitching centre to the mobile switching centre of the calledsubscriber.
 11. A method as claimed in claim 7 or 8, wherein a new pairof messages are formed for transmitting the information on the serviceswitching point connected to the mobile switching centre of the callingsubscriber and a service program related thereto, in whicha firstmessage contains an interrogation sent by the mobile switching centre ofthe called subscriber to the mobile switching centre of the callingsubscriber on whether the calling mobile switching centre requires theinformation on the location cell of the called subscriber, and a secondmessage is sent by the mobile switching centre of the calling subscriberto the mobile switching centre of the called subscriber when the firstmessage contains the information relating to the service control pointand a related service program.
 12. A method as claimed in claim 1,wherein the information on the location cell of a called subscriberdescribes a cell in which the called subscriber is located and theservice control point connected to the mobile switching centre of thecalling subscriber analyses whether said cell belongs to the group ofcells.
 13. A method as claimed in claim 12, wherein when the informationon the location cell of the called subscriber provides a result of theanalysis on whether the location cell of the called subscriber belongsto the group of cells, the service control point connected to the mobileswitching centre of the called subscriber makes said analysis.
 14. Amethod as claimed in claim 1, wherein the numbers in the restrictedsubscriber group are private numbers, and the private number of thecalled subscriber is converted into a subscriber number at the beginningof call setup.
 15. A method as claimed in claim 12, wherein a PBXexchange or part of a PSTN/ISDN network is set as a virtual cell, and,when the subscriber number analysis of at least one of the subscribersproves that the subscriber is a subscriber of the PBX exchange or a partof said PSTN/ISDN network, the charging criterion is applied.